Sponge reef maybe

[0lderthandirt]

This is my property, about 100 acres total. About 25 miles south of grand canyon and just 6 miles from grand canyon caverns at 5400 feet elevation. The first picture is a hill just outside my door, take the dog up this everyday when we go for our walk. Every rock in this picture has fossils on them. An example is the second picture. About 1/8 mile into the trees there is a trail I've made over the years with the quad. I've just recently realized a section of that trail  is  like  an ancient seabed. All red ,airy rocks -light but hard to actually break. Every rock you pick up is embedded with fossils, mostly shells I think. An example is the third picture. I'm thinking this was perhaps a sponge/coral reef because of all the tiny holes or was this just sediment? Any thoughts or comments would be most appreciated. Thanks

(Oops, wasted too much memory on that hillside,  will post red rock separately )

This is the example of the red rocks that make up the trail

[Virgilian]

Looks like Paleozoic Era material to my eye. I don't see any overt evidence of Porifera in the rocks photographed. The Permian Kaibab Limestone that forms the rim of Grand Canyons sometimes contains chertified sponge blobs referred to the genus Actinocoelia.

 

Somebody more familiar with local Arizona statigraphy will have to chime in here.

[0lderthandirt]

I think of the chert as glassy red stuff, like flint, and i find that in the limestone. Am I understanding this correctly that the lightweight spongelike rock becomes that dense red, somewhat translucent, chert?

[ynot]

9 minutes ago, 0lderthandirt said:

I think of the chert as glassy red stuff, like flint, and i find that in the limestone. Am I understanding this correctly that the lightweight spongelike rock becomes that dense red, somewhat translucent, chert?

Chert and flint are cryptocrystalline quartzites that form in sedimentary type rocks. Both are colored by trace minerals in their structure and can be any color (red is from iron.). 

As water percolates through the bedrock it takes silica and concentrates it into a nodule.

The porous nature of Your bedrock could be caused by the removal of the silica during the formation of the chert.

[0lderthandirt]

Very interesting, that makes sense. Porous - that's the word i couldn't think of! 

[Virgilian]

6 hours ago, 0lderthandirt said:

This is my property, about 100 acres total. About 25 miles south of grand canyon and just 6 miles from grand canyon caverns at 5400 feet elevation.

 

Just consulted some online county geologic maps of Arizona.

 

Based on your locality description, you should be sitting right on top of what's mapped as the Paleozoic Devonian-Mississippian Martin Limestone (Devonian) and Redwall Limestone (Mississippian) undifferentiated. The nearby Grand Canyon Caverns are carved in the Mississippian Redwall Limestone, of course.

[Arizona Chris]

Looks like Mississippian Red wall limestone, mooney falls member.  The second image shows a typical fossiliferous chert - the tiny holes are microfossils including crinoid stems, forams and small gastropods and ostracods.  I have no idea what the first image shows, looks to me like a cemented limestone breccia like rock.  Could also be some sort of weird weathering pattern.